Considerable progress has been made in the last several years in increasing the sugar yield by improving the varieties being planted, enriching the soil with fertilizers and irrigating the soil in climates which do not naturally provide sufficient moisture for optimum plant growth. More recent efforts in improving sugar production have increasingly turned toward the use of chemicals in modifying and controlling the physiological processes of sugarcane, particularly in ripening prior to harvest. See U.S. Pat. Nos. 3,224,865; 3,245,775; 3,291,592; 3,482,958; 3,482,959; 3,492,961; and 3,493,361.
With some compounds previously suggested for this purpose there has been some concern about their resistance to breakdown in the plant and their persistence in the soil when the intended use of the sugar is nutritive as opposed to industrial (e.g., in fermentation processes). Consequently, extensive efforts continue to be made in searching for physiologically harmless or rapidly degradable chemical agents that can be effectively used to modify the ripening of sugarcane so as to increase the sucrose yield therefrom.
Generally speaking, chemicals selected for evaluation have been of types which have been previously found active in work with other plants as plant hormones, herbicides or inhibitors of growth of terminal buds, or active in killing the spindle of cane upon topical micro-application, etc. However, among the compounds heretofore found to be useful for such other special purposes, very few have been found effective in controlling the ripening of sugarcane in the desirable manner. No relationship has been recognized to date between the chemical structure of such compounds and (a) their phytotoxic effects, (b) their physiological effects on the morphogenetic development of the plant, and (c) their activity in having positive effects on ripening. In other words, the effectiveness of a compound in controlling the ripening of sugarcane and thereby increasing sugar yield remains essentially unpredictable, and the search for suitable agents continues to be fundamentally empirical.
A review of the literature discloses that some work has been done using surfactants to increase the crystallization rate of cane sugar and in the purification of sugar juices. See Ramaiah et al, Proceedings, 29th Annual Convention of the Sugar Tech. Assoc. of India, 1961, Part II. Some of the surfactant compounds of the present invention have also been used in very minor, i.e., surfactant, amounts simply as wetting agents in applying an active ingredient such as a benzoic acid compound to cane stalks for sugarcane ripening. See, for example, U.S. Pat. No. 3,224,865 wherein ethoxylated alcohol surfactants are used as wetting agents. However, surfactants produced by the ethoxylation of phenols or higher alcohols have not been recognized as useful per se as sugarcane ripening agents. Ethoxylated phenol and higher alcohol nonionic surfactants are available commercially, and are regarded as materials of only slight to moderate oral and skin penetration toxicity. Such compounds have been exempted by the Food and Drug Administration from tolerance requirements when used in or on raw agricultural commodities (see Federal Register, Vol. 35, No. 161, Aug. 19, 1970).
It is an object of this invention to provide new agents for controlling the ripening of sugarcane. A more specific object is to increase the sucrose yield of sugarcane by chemically treating it during its final ripening stages prior to harvest without introducing substantial toxicological hazards, and preferably without causing visible (phytotoxic) damage to the cane plant, such as drying of the spindle or other leaf.
Still more specifically, it is an object of this invention to increase the sucrose yield of sugarcane by treating it prior to harvest with a chemical agent which is sufficiently stable to provide the desired effect over a period of several weeks and thus give adequate operational flexibility, but which has a relatively low degree of persistence in the soil and is susceptible to decomposition by soil bacteria.